Protect yourself against future threats.
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AUSCERT External Security Bulletin Redistribution
ESB-2010.0271
Denial of Service in SPNEGO - MIT krb5 releases krb5-1.7 and later
25 March 2010
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AusCERT Security Bulletin Summary
---------------------------------
Product: MIT krb5 releases krb5-1.7 and later
Publisher: MIT Kerberos Team
Operating System: UNIX variants (UNIX, Linux, OSX)
Impact/Access: Denial of Service -- Remote/Unauthenticated
Resolution: Patch/Upgrade
CVE Names: CVE-2010-0628 CVE-2009-0845
Reference: ESB-2009.0342
ESB-2009.0304
Original Bulletin:
http://web.mit.edu/kerberos/www/advisories/MITKRB5-SA-2010-002.txt
Comment: Please note as the vendor states:
"This is an implementation vulnerability in MIT krb5, and not a
vulnerability in the Kerberos protocol."
The vulnerability is scheduled to be correcting in upcoming releases
but a patch has been made available in the meantime.
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MITKRB5-SA-2010-002
MIT krb5 Security Advisory 2010-002
Original release: 2010-03-23
Last update: 2010-03-23
Topic: denial of service in SPNEGO
CVE-2010-0628
VU#839413
denial of service in SPNEGO
CVSSv2 Vector: AV:N/AC:L/Au:N/C:N/I:N/A:C/E:POC/RL:OF/RC:C
CVSSv2 Base Score: 7.8
Access Vector: Network
Access Complexity: Low
Authentication: None
Confidentiality Impact: None
Integrity Impact: None
Availability Impact: Complete
CVSSv2 Temporal Score: 6.1
Exploitability: Proof-of-Concept
Remediation Level: Official Fix
Report Confidence: Confirmed
SUMMARY
=======
In MIT krb5 releases krb5-1.7 and later, the SPNEGO GSS-API mechanism
can experience an assertion failure when receiving certain invalid
messages. This can cause a GSS-API application to crash.
This is an implementation vulnerability in MIT krb5, and not a
vulnerability in the Kerberos protocol.
IMPACT
======
An unauthenticated remote attacker could cause a GSS-API application,
including the Kerberos administration daemon (kadmind) to crash.
AFFECTED SOFTWARE
=================
* kadmind in MIT releases krb5-1.7 and later
* FTP daemon in MIT releases krb5-1.7 and later
* Third-party software using the GSS-API library from MIT krb5
releases krb5-1.7 and later
* MIT releases prior to krb5-1.7 did not contain the vulnerable code.
FIXES
=====
* The upcoming krb5-1.7.2 and krb5-1.8.1 releases will contain fixes
for this vulnerability.
* Apply the patch available at
http://web.mit.edu/kerberos/advisories/2010-002-patch.txt
A PGP-signed patch is available at
http://web.mit.edu/kerberos/advisories/2010-002-patch.txt.asc
REFERENCES
==========
This announcement is posted at:
http://web.mit.edu/kerberos/advisories/MITKRB5-SA-2010-002.txt
This announcement and related security advisories may be found on the
MIT Kerberos security advisory page at:
http://web.mit.edu/kerberos/advisories/index.html
The main MIT Kerberos web page is at:
http://web.mit.edu/kerberos/index.html
CVSSv2:
http://www.first.org/cvss/cvss-guide.html
http://nvd.nist.gov/cvss.cfm?calculator&adv&version=2
CVE: CVE-2010-0628
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2010-0628
CERT: VU#839413
http://www.kb.cert.org/vuls/id/839413
ACKNOWLEDGMENTS
===============
Thanks to Nalin Dahyabhai, Jan iankko Lieskovsky, and Zbysek Mraz (all
from Red Hat) for discovering and reporting this vulnerability.
CONTACT
=======
The MIT Kerberos Team security contact address is
<krbcore-security@mit.edu>. When sending sensitive information,
please PGP-encrypt it using the following key:
pub 2048R/8B8DF501 2010-01-15 [expires: 2011-02-01]
uid MIT Kerberos Team Security Contact <krbcore-security@mit.edu>
DETAILS
=======
A patch to fix CVE-2009-0845 interacted poorly with new functionality
introduced in krb5-1.7. This allowed an error condition to occur
where receiving an invalid packet could cause an assertion failure,
crashing the program and causing denial of service.
When the spnego_gss_accept_sec_context() function (in
src/lib/gssapi/spnego/spnego_mech.c) receives an invalid packet during
the beginning of a GSS-API protocol exchange, it can set some internal
state that tells it to send an error token without first creating a
context handle, but some subsequently executed code contains a call to
assert() that requires that the context handle be non-null.
REVISION HISTORY
================
2010-03-23 original release
Copyright (C) 2010 Massachusetts Institute of Technology
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